List of top Physics Questions

: Zener diode works on principle of breakdown voltage. :Current increases suddenly after breakdown voltage.
Work done by friction over a closed path is not zero and no potential energy can be associated with friction. Every force encountered in mechanics have an associated potential energy.
When distance between two bodies is doubled and also mass of each body is doubled, gravitational force between them remains the same. According to Newton?? law of gravitation, force is directly proportional to product of the mass of bodies and inversely proportional to the square of the distance between them.
: When a light wave travels from a rarer to a denser medium, its speed decreases. The decrease in speed imply a reduction in energy carried by the light wave. : The energy of a wave is inversely proportional to velocity of wave.
: The radius of curvature of a mirror is double of the focal length. : A concave mirror of focal length $f$ in air is used in a medium of refractive index $2$. Then the focal length of mirror in medium becomes $2f$.
The position-time graph of a body moving uniformly in a straight line is parallel to position axis. The position-time graph in a non-uniform motion gives constant velocity at all instants of time.
The motion of a particle under the central force is always confined to a plane. Angular momentum is always conserved in the motion under a central force.
The motion of a ceiling fan is rotational only. The motion of a rigid body which is pivoted or fixed in some way is rotation.
The moment of inertia of a rigid body depends only on the mass of the body, its shape and size. Moment of inertia $ I = MR^2$, where $M$ is the mass of the body and $R$ is the radius vector.
The mass of $\beta$-particles when they are emitted is higher than the mass of electrons obtained by other means. $\beta$-particle and electron, both are similar particles.
The flow is turbulent for Reynolds number greater than $2000$ Turbulence dissipates kinetic energy in the form of heat
: The images formed by total internal reflections are much brighter than those formed by mirrors or lenses. : There is no loss of intensity in total internal reflection.
: The fringe closest on either side of the central white fringe in case of interference pattern due to white light is red and the farthest appears blue. : The interference patterns due to different component colours of white light overlap.
: The electrons in the conduction band have higher energy than those in the valence band of a semiconductor. : The conduction band is above the energy gap and valence band lies below the energy gap.
The dimensional formula of surface energy is $[M^1L^2T^{-2}]$. Surface energy has same dimensions as that of potential energy.
: The conductivity of an intrinsic semiconductor depends on its temperature. : No important electronic devices can be developed using intrinsic semiconductors.
: The bridges declared unsafe after a long use. : Elastic strength of bridges loses with time.
The centre of gravity of a body coincides with its centre of mass only if the gravitational field does not vary from one part of the body to the other. Centre of gravity is independent of the gravitational field
:The centre of mass of a body may lie where there is no mass. The centre of mass has nothing to do with the mass.
The back emf in a dc motor is maximum when the motor has just been switched on When motor is switched on it has maximum speed
The accelerated motion of an object may be due to change in magnitude of velocity or direction of velocity or both. Acceleration can be produced only by change in the magnitude of the velocity.
: Sun looks reddish at sunrise and sunset. : Sun rays have to pass through a larger distance in atmosphere.
Pascal?? law is the working principle of hydraulic lift Pressure $= \frac{thrust}{arer}$
Moon has no atmosphere. The escape velocity for moon is less than that for earth.
Magnetic lines of force form continuous closed loops Magnetic poles always occur in pairs as north pole and south pole